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resistance is directly proportional to wire length and inversely proportional to wire cross-sectional area. In other words, If the wire length is doubled, the resistance is doubled too. If the wire diameter is doubled, the resistance will reduce to 1/4 of the original resistance. =======================Yeah...but what's the factor???

Actually resistance is directly proportional to the length provided area remains constant. But as we stretch the wire only its volume would remain constant. So its area is to …be decreased as length increases. V = pi r^2 * L Now we have R = K * L / pi r^2 Multiplying numerator and denominator by L we get R = K/V * L^2 So resistance is found to be proportional to square of length Hence as length gets increased by 2 times, its resistance value would increase by 4 times. (MORE)

If you are going to install new wiring and outlets, then there are three different methods of receptacle wiring that you can do. Two of them are considered quite acceptable an…d electricians, electrical inspectors, and the NEC heavily frown on the third. Choosing the best way to do the job is often based on how many wires are in the box, how many outlets are wired in the same circuit, and who is doing the work. Single outlet wiring is very simple, but here is a look at all three forms of through wiring.When you have only one set of wires going into an outlet box, this is a simple task to wire. You only have to connect to the screw terminals on the outlet in the appropriate manner and the job is done. Through wiring, a receptacle involves an incoming wire known as the line and an outgoing wire known as the load. This is done in rooms where several outlets are connected to the same branch circuit. It makes wiring all of the outlets much easier and saves on wire. Outlets are made with two sets of hot and neutral terminals to facilitate through wiring, making installation far easier. However, this does not necessarily make using both terminals the best way.Pigtail wiring is considered by the NEC and most professional electricians to be the best form of through wiring. In order to wire in an outlet using this method, you strip back the insulation on two identical wires and twist them together with a third length of wire, securing them with a wire nut. The single wire is then placed under the appropriate screw. Not only does this reduce the amount of resistance on the wiring, but also, even if the outlet is removed from the circuit, the current will continue to flow. No other form of wiring works this way.Feeding through the outlet itself is by far the most common form of through wiring in use. This involves using the outlet itself as the junction between the line in wires and the load out wires. One set is attached to the terminals behind one of the outlets, the other to the terminals behind the other outlet. The ground wires are then twisted into a pigtail and connected to a single ground screw. Because the outlet is now in the middle of the circuit, if it fails or if there is a problem, then the outlets on the load side will also experience similar issues. In addition, because each outlet adds a certain amount of resistance into the circuit, the more outlets on the line, the larger the voltage drop will be by the time that you get to the last outlet on the branch.Despite the fact that most modern outlets are designed to be back wired, no professional electrician would consider using this method. In the back of the outlet there are four small holes, inside of which is a copper strip under tension. The idea is to strip a short length of insulation from both the black and white wires. The stripped ends are then pushed into the holes and the copper strips are intended to hold them firmly in place. While this is a very fast way to install the wires, even the NEC does not recommend this method of wiring.Because many outlets are made to be back wired, there must be a reason why the use of this method is not recommended. The problem is that although the tensioned copper strips are supposed to hold the wire securely in place, wiring a receptacle in this manner is considered dangerous. The tension strips are not likely to hold the wire firmly in place, leading to arcing and high levels of resistance. This can and frequently does lead to overheating and fires. The only time back wiring is advisable is if the wires being fed into the back of the outlet are going to be held in place by screw clamps.Wiring in a new receptacle can be a very simple task. However, if you are installing a new outlet in a branch circuit with two or more outlets, then the method of through wiring that you choose will make a big difference in both efficiency and safety. The best possible method to use is pigtail wiring, which reduces the number of wires attached to the receptacle. Electricians recommend that you never use the back wiring holes on an outlet as this will increase your risk of fire from overheating and arcing.When wiring outlets, you must adhere to the NEC color code. The black or hot wire must always be connected to the brass colored screw terminal. The white or neutral wire must always be connected to the silver screw terminal, and you should never forget to attach the bare or ground wire to the ground screw on the outlet.(MORE)

Wire sheathing is the insulating cover that encompasses wire. There are 11 types of wire sheathing. They are identified by a standard code. The code identifies the insulation …by materials, appearance, durability, and application. The National Electrical Code (NEC), as well as local building codes, regulates the types of wire and cable that can be used in specific electrical applications, as well as the manner of installation.The Insulation Code is the criteria set by the NEC. It outlines sheaths by material, appearance, durability, and application by ratings. Each sheath indicates at a glance the advantages and disadvantages of using that specific wire for a specific application. The exterior type of insulation in conjunction with the interior conductors dictates the possible applications. The materials used are plastic, nonmetallic, metal and glass braid.The color of the sheathing is very important. Colored insulated wires, except for white and green, are always hot. In residential wiring, black, blue, and red sheaths identify hot wires. White sheaths indicate that a wire is neutral. Green sheaths and bare copper wires indicate that it is a ground wire. If the sheath is metal then it is used as the grounding mechanism.The durability issues are rated as Excellent, Good, Fair, or Poor. The issues rated are temperature range, abrasion resistance, flexibility, and water submersion. The overall ratings are one component in determining the applications possible. The other component to be considered is the resistance to specific exterior conditions. These are resistance to solvents, acid, base and open flame. For example, excellent across both the Identification and Application Guide and Resistance Guide by a plastic sheath over bare wires within a glass braid jacket would identify the wire as usable for single measurement length to 343 degrees Celsius.There are actually multiple wire insulation selection charts. Some categorize the selections by type, others by advantages and disadvantages. These charts consider the sheaths' materials, ratings and the wire's gauge rating to distinguish the areas that are approved for installation. There are also charts that tell you whether it is for dual use. Always consider the coding in your area when you are selecting wiring for any installation.The type of sheathing is crucial to the installation applications. As far as nonmetallic-sheathed cable goes, the color denotes the use based on all of the collected information. For example, gray-colored nonmetallic-sheathed cable is more related to installation than wire size. It is used for underground installations. It is water-resistant. It can also be resistant to oil and sunlight.Wire sheathing has a language all its own. The material and colors indicate multiple things. Applications and where it can be installed are apparent at a glance. Qualities such as durability and resistance to a range of exterior conditions determine the sheathing needed.Dupont's Teflon technology is familiar in the kitchen. Teflon, combined with Kapton, is also used in wire sheathing. It is known for its thermal and electric conduction. Kapton is the lightest weight of the wire insulation materials. In addition, it also offers cut-through resistance and radiation resistance.(MORE)

When you talk to most experienced electricians, they will tell you that Cu (Copper) wire is the only safe choice for use in residential applications. While this may or may not… be the case, copper wiring is currently the most commonly used. Although modern aluminum wiring is considered perfectly safe for electric circuits in homes, previous experiences with this product in the 1970s has left most electricians leery of using it. Poorly made aluminum wiring from this period has been responsible for countless home fires and hundreds of deaths.When it comes to electric wiring, silver offers better conductivity when it is compared to copper wire. At the same time, copper provides the ability to handle a wide load range when compared to other non-precious metal wires. This makes it possible for manufactures to use less armoring or insulation in its manufacture. Copper has a much higher heat resistance, reducing the risk of overheating due to high loads. It is also far more resistant to corrosion and what little patina forms will not affect its performance in any way.Of all the non-precious metals, copper is the only one capable of being manufactured into strands which are no thicker than a strand of human hair. Because it is so malleable, these thin strands can be bent into practically any shape without the fear of them breaking. This can be seen in the windings of many miniaturized motors. You can also see this in the micro thin wires in modern headphones, as the thin wires can be twisted into very small rolls without breaking. Copper can also be used to create very large cables for any number of applications.As you shop in your local electrical supply store, you will find devices such as switches and outlets marked as "Copper Only" or CO/AL R. These devices are marked this way for a reason. Because copper and aluminum contract and expand due to heat, it is important you buy devices made for the type of wiring your home has. If you try to use copper only outlets or switches with aluminum wiring, you run the risk of overheating and fires. This is because as the aluminum wires contract and expand in and copper only fixture, they will work loose increasing the resistance in the circuit. This causes the connection point to overheat.If your home has aluminum electric wiring throughout, there is no need to panic. Start by looking at the year your house was built. If it was built in the late 1960s or the early 1970s, you may have a problem. These are the only years when the poor quality aluminum wires were used. After this, most builders went back to copper. In the last few years a new and very safe aluminum cable has been developed. If you are not sure, you can have a licensed electrician go over the wiring in your home.The only place where Cu wire is not a good choice is in devices where low voltage or low current flow is anticipated. Despite the fact it is an excellent conductor, copper wiring does not perform well in this type of device. For this reason, gold and silver are considered to be a much better choice. Copper is incapable of helping to control surges of electricity when drawn into tiny wires. On the other hand, precious metals such as silver and gold can handle them quite well.The only real reason copper has ever been replaced as residential wiring has been cost. During the early 1970s, the choice to use aluminum proved to be deadly for hundreds who died due to fires caused when this type of wire overheated. Modern aluminum cables no longer create this type of situation as their composition has been changed significantly. However, you still should never try to use any device labeled as Cu wire only with aluminum wiring as this is not safe.If you live in a house with aluminum wiring instead of copper, you may not need to have it all ripped out and replaced. As long as all of the connections are properly secured, there should not be any problems. However, you should have them checked by a professional on a regular basis to be sure they do not become loose.(MORE)

If you have the experience regarding electrical wiring and installation, connecting electrical wires is not a difficult task. However, despite all the training and experience,… mistakes do happen. These mistakes can either be harmless or can cause serious accidents. To avoid this, here are some tips you can use as a checklist to refresh your memory.The purpose of junction boxes is to protect your electrical connections from any damage. Any exposed wire can result in a loose connection leading to short circuit. Therefore, it is logical not connect your wires outside the junction box. If your connections are not installed in an electrical box, you can install a box and just reconnect the wires again. It can be extra work for you but it is much better than spending more if any accidents happen because of a short circuit.The electrical code requires at least six inches of wire outside the electrical box at the back and three inches at the front. Giving an allowance when connecting electrical wires makes it easier to connect and fix it. On the other hand, short wires can be dangerous. If you encounter short connections, you can still solve this by installing wire connectors, which you can buy at hardware stores. These types of connectors are also used when installing wires in difficult spots.Aside from the length of wire connections, the electrical code also requires cables placed under wall or ceiling framing to be thoroughly protected. This is because exposed cables in these areas are vulnerable and prone to damage. You can protect these cables by placing at least a 1 1/2 -inch thick board alongside the wires. Secure the board with a screw or a nail, but there's no need to staple the wire to the board.If outlets and switches a poorly supported, they can get loosely connected. When this happens, the switches or outlets can also loosen the wires as they move when you touch or use them. The loose wires are potential fire hazard because they can overheat. Fix these loose outlets by placing special placers under the screw to keep them tightly in place. You can also wrap a coil around the screw to tighten it or buy a small washer and place them under the screw.Three-slot outlets are very useful, especially if you have devices or electric appliances with three-prong plugs. However, you should always remember that before you begin connecting wires using three-slot outlets, there should also be a ground available. If you are not sure whether they are grounded correctly, use a tester and the lights will indicate whether there is a fault or the connection is correct. If there is a three-slot outlet in your house without a grounded box, simply replace it with a two-slot outlet.Another mistake most often made when connecting electrical wires is attaching electrical boxes near combustible materials without any protection. Doing so can expose these materials to potential sparks or heat that can result in fire. It is a requirement of the electrical code is to flush all electrical boxes from walls made of wood and similar combustible materials. To solve this problem and avoid the possibility of fire, install a plastic box extension to prevent the wires from making contact into the wood. You can also use a metal box extension but make sure to attach it to the ground wire with a short piece of wire and a grounding clip.When connecting electrical wires, especially on ceilings, you must use a cable clamp to hold them in place. Cable clamps not only keep the wires in place, but they also keep the connections from straining. If there is no clamp, the sharp edges of a metal box can cut the wires as time goes by. Even wires installed in plastic boxes need a clamp. Some electrical boxes have already built-in clamps when you buy them, but some don't. You can always buy approved cable clamps at a hardware or home store. Just make sure that when you place the wires inside the clamp, let at least 1/4 inches of sheathing be visible inside the box.Do not try to overstuff all the wires in a small box when installing your wire connections. The electrical code has a guideline about the minimum size of electrical box you can use. To figure out how big your electrical box should be, count the items in your box giving one point for each hot and neutral wire that you will place in the box. You should also give one point each to the combined ground wires and cable clamps while devices, like outlets and switches, receive two points. After that multiply the total by two if you're using 14-gauge wires and by 2.25 if you're using 12-gauge wires. Then choose an electrical box that can hold the total volume of the wires and devices. You'll find the capacity of plastic electrical boxes stamped inside, while the electrical code has specifications for metal boxes.Connecting electrical wires require care to prevent accidents and fire hazards. You should always keep the guidelines in mind and use approved materials to lessen the risks. If you find faulty wiring or connection in your home, immediately fix them before it's too late. And if you're in doubt, you can check the electrical code or ask an expert to do the repairs and installation.If outlets and switches a poorly supported, they can get loosely connected. When this happens, the switches or outlets can also loosen the wires as they move when you touch or use them. The loose wires are potential fire hazard because they can overheat. Fix these loose outlets by placing special placers under the screw to keep them tightly in place. You can also wrap a coil around the screw to tighten it or buy a small washer and place them under the screw.(MORE)

Electricians know the importance of using the correct wiring when working on an electrical system. The wrong wire can lead to circuit overloads and possibly fire. During train…ing, an electrical apprentice will learn the various types of electric wire and when it is used in the overall electrical system. These wires must be understood in order to pass the tests required to be a certified electrician.Triplex wire is a three-strand aerial cable that is used by utility companies to feed the power pole. These wires tie to wires that are coming from the weather head. Two of the three wires are individually insulated then twisted together with the third bare wire, and covered with a protective sheath. The bare wire is the grounding wire. This type of wire is typically installed in overhead applications from pole to pole.The wires that connect homes to power poles are called main feeder wires. The size of these wires is large enough to add to the electrical load without replacing the main feeder wire. The capacity of the wire is determined by the distance the wire is spanning. Long distances can cause the voltage to drop and the current to rise. This can ultimately lead to damage to the insulation and electrical issues.Wires that feed the breaker panels and main junction box in the home are called panel feed wires. The wires are sized to handle 25 percent more than the panel they are feeding. For example, if the panel is 100 amps, the wire feeding it should be 125 amps. The wiring in the panel branch off and feed the house and so they must be higher than the panel to handle the added loads that occur as they branch off. These wires are similar to the main feeder wires in that a thermoplastic heat-resistant nylon coated wire coats them.Nonmetallic sheathed wires are sometimes known as Romex wires. This is a two or three wire bundle that contains one neutral wire that is bare and one or two conducting wires in plastic insulation. This is the wire in the house that feeds power to the load. It is an inexpensive wire that is usually 15, 20, or 30 amps. It is also available with a metal sheath but is called BX or armored cable in that form.Single strand wire is comprised of one piece of copper wire rather than many pieces of wire stranded together. It is not as flexible as stranded wire but is stronger. Solid wire does not have the problems associated with being made of multiple strands when it comes to sizing. The diameter of single strand wire does not change regardless of the tension placed on it. However, because it is not flexible, it can break if bent and flexed over time. Single strand wire is less expensive and should be used when the wire is going to be put in place and not moved. If there is a possibility of the wire moving or flexing, stranded wire should be used.Learning these types of wires and when they are used is part of training to be an electrician. It is important for safety reasons and to ensure that power is properly supplied through the application. Electricity must be respected and installed properly to prevent fire and electrocution. Working with a master electrician to learn the various types of wiring provides hands-on experience that will be valuable during a career as an electrician.Never try to determine what type of electrical wire is in a house or box until you are certain that the wires are not live. Any do-it-yourselfer should own a non-contact voltage detector. This should be used on every wire in a box to ensure that no power is coming through any wires. It doesn't take but one live wire to cause injury or even death.(MORE)

Beautiful wire bracelets can be made from many different mediums. A wire bracelet can be made totally from wire or can have beads and other items on it. The bracelet can be ma…de from silver, copper, or gold wire. You can also use red, green, yellow, and pink wire to make your bracelets. Bracelets from wire can be woven, crocheted, braided, twisted, or the beads just strung on them.Take a piece of wire about four inches longer than the size you want your bracelet. Put the wire through one of the parts of your clasp. then wrap the shorter end of the wire around the other side of the wire, capturing the clasp inside. Wrap the end around about three times, clip the end close to the other wire, and then crimp the end in close. This makes it so that the person wearing the bracelet does not get scratched. String your beads and spacers in the order you wish them to be. Put the other end of the clasp onto the wire and leave room to wind the wire around three times. Wind the wire, cut it close to the other wire, and then crimp the loose end.To do this bracelet, you will need a crochet hook, about size G. Cut two to three pieces of wire about ten inches longer than you want the bracelet. Take the first piece of wire and wind it around the crochet hook about four inches from the end. Take the wire back to itself and then wind it around about three times. Leave the end for now. Do a chain stitch with the crochet hook and the wire. The chain stitch is just drawing the wire up through the last loop. Then go down and pick up the wire and draw it through again. When you get about four inches from the end, you just draw the wire completely through the end loop. You can add beads as you crochet if you wish. Do the same for the other wires. Once you have all of them crocheted, you take them and put them together. If you have two wires, you just twist them. If you have three you can braid them. Then connect them to the two sides of your clasp.Take three or more strands of wire that are about twice the length you want the bracelet. Twist them together about three inches from one end. Then fasten that end to a board or any anchor that will hold the end tightly for you. If you are going to braid them, just start braiding, taking care to keep your braid smooth if you want it even. However, uneven braiding or weaving can be part of the beauty. Once you get to the length of bracelet you want, then attach the other wire to the other end of the clasp. You can do a lot of the weaving patterns used in macrame books if you want to weave the wire. Just be careful to keep the wire from becoming kinked during the process.Take two to 20 pieces of wire about twice as long as you want the finished bracelet to be. Twist them together about two inches from the end of the wires. Fasten the wire to a board or something to hold it securely. Then, twist the wires. Twist until you have them as tight as you want. Attach both ends of the wire to a part of a clasp. You can also buy a machine that will twist the wires for you. Sometimes the machine does a more even job than doing it manually.Woven bracelets are done with two different gauges of wires. You will need a larger gauge for the two outside wires and a thinner one to go between them. Cut the two larger wires about three inches longer than you wish the finished bracelet to be. Take the smaller wire and wrap it three times around a larger one about an inch from the end. Then take that same smaller wire and wrap it around the other larger wire once. Weave your smaller wire back and forth between the two larger wires, until you have the length you want. Twist all three wires together and attach to a clasp. Twist the two large wires together on the other end and attach to the other piece of the clasp.Wire bracelets are fun to make and wear. You can make them from red, green, copper, gold, or silver wire. You can weave, braid, crochet, twist, or even just string the wire with your favorite beads. You can add beads to the woven, braided, and twisted bracelets too. Wire bracelets are easy to make and look great when you wear them.When working with wire, you can also use crimp beads to fasten the ends. The crimp beads are a little pieces of metal you put over both ends and then squeeze together. This keeps the ends of the wire away from the wearer and keeps them tight.(MORE)

A piece of wire stretched such that its length increases and its radius decreases will tend to have its resistance increase. The formula for this is: R = ρL/A where ρ = re…sistivity of the material composing the wire, L = length of the wire, and A = area of the conducting cross section of the wire. It can easily be seen that as area decreases resistance gets higher. In the case proposed the wire length is not reduced as it is stretched to reduce the area, this increases the resistivity as well. (MORE)

Total resistance in the circuit decreases Two resistors in parallel have less overall resistance than the same two resistors in series, or even just one of the resistor…s by itself. This is because two resistors in parallel draw more current than just one resistor -- assuming constant voltage. If the voltage remains constant and the current increases, then Ohm's Law (V=IR) dictates that the resistance must decrease. When you have resistors in parallel, you can compute the total resistance fairly easily with simple math. The special case of having two resistors in parallel is interesting and easy to remember. To compute the total (or apparent) resistance of two resistors in parallel, just divide the product of the resistance values by their sum. Let's say you've got a 3-ohm resistor in parallel with a 6-ohm resistor. The total resistance is 6*3/(6+3) = 18/9 = 2. So, the total resistance of those two resistors in parallel is two ohms. If you've got two identical resistors in parallel, the resistance is exactly half the value of one resistor. Two 10-ohm resistors in parallel have a resistance of five ohms. Two 100-ohms resistors have a resistance of 50. Two 150Kohm resistors have a value of 75Kohm. If you've got a bunch of resistors in parallel, here's what you do. Add up all the reciprocals of the resistance values. Then find the reciprocal of that sum. Your answer should be less than the lowest-valued resistor in your R-ladder. If it's not, you hosed the calculation. Try the following: Calculate the resistance of the following resistors in parallel (assume ohms for each): 2, 4, 8, and 16. You should come out with 16/15 ohms, which equals 1.067 ohms. I know some of you want to see the math. First, add up the reciprocals: 1/2 + 1/4 + 1/8 + 1/16 = 8/16 + 4/16 + 2/16 + 1/16 = 15/16. Next, take the reciprocal of that answer: 16/15 = 1 and 1/15 = 1.067 ohms. If you need more help, use the discussion page, but leave a note on Schnazola's personal page so I know to look. (MORE)